The field of Ellipsometer and the like is well known. Generally a beam of electromagnetic radiation is directed to interact with a sample and the enter a detector where a change in it's polarization state, based on said interaction with said sample, is determined. Said change is related to optical and physical properties of the sample. Typically, samples that are investigated have generally planar surfaces, but this is not always the case. At times it is of interest to, for instance, investigate items that have a non-planar shaped surface during manufacture thereof to ensure that over a sequence of such items manufacturing parameters are being properly maintained. In such cases a system that would allow a quick change of items from “off”, to “on” an investigation system stage, along with quick determination of ellipsometric parameters associated therewith, would provide utility.
A number of Patents that are Assigned to the J.A. Woollam CO., Inc. provide insight to elements that such a system might include. For instance, U.S. Pat. No. 7,872,751 to Liphardt et al. describes a system for quickly setting angle of incidence (AOI), plane of incidence (POI) and Height, (of ellipsometer elements above a sample), parameters in a mapping ellipsometer or the like. U.S. Pat. No. 7,136,162 describes a system for aligning a beam to a sample surface at a known angle-of-incidence (AOI). U.S. Pat. No. 7,746,471 to Johs et al., and U.S. Pat. No. 8,339,603 to Liphardt et al. describe Flying and Mapping Ellipsometer Systems with applications to investigating the inside of a planar or non-planar tubular shaped object and to looking between two plates in a more linear system, respectively. U.S. Pat. No. 7,623,237 to Liphardt et al. and U.S. Pat. No. 8,467,057 to Johs et al. describe sample investigation and ellipsometer systems etc. that provide both a source of an electromagnetic beam, and a Detector thereof on the same side of a sample. A reflector serves to direct electromagnetic beams that impinge onto a sample back in the general direction from which they came as they approached said sample. While a Patent to Svetkoff et al., U.S. Pat. No. 6,028,671, was identified in a computer search for Patents containing the words “Concave Object” and “Ellipsometry”, no Patents relevant to the present invention were identified in said computer search.
While the cited Patents arguably demonstrate elements of sample investigation systems that can be selected and modified, while rejecting other elements therewithin, there remains need for a specific system that would allow quickly and easily determining average ellipsometric parameters that correspond to data obtained from two locations on a concave object. One example of an applications for such a system would be in sequential monitoring of a series of manufactured tire rims, which, it noted, do comprise concave shapes.